Aluminium substitution in Sb2S3 nanorods enhances the stability of the microstructure and high-rate capability in the alloying regime

Abstract

Alloy anodes, with twice the capacity of graphite, are promising for next-generation lithium-ion batteries (LIBs). However, poor rate-capability and cycling stability, mainly due to pulverization, have limited their application. By constraining the cutoff voltage to the alloying regime (1 V to 10 mV vs. Li/Li⁺), we show that Sb_1.9Al_0.1S₃ nanorods provide excellent electrochemical performance, with an initial capacity of ∼450 mA h g⁻¹ and excellent cycling stability with 63% retention (capacity ∼240 mA h g⁻¹ after 1000 cycles at 5C-rate), unlike 71.4 mA h g⁻¹ after 500 cycles observed in full-regime cycling. When conversion cycling is also involved the capacity degrades faster (<20% retention after 200 cycles) irrespective of Al doping. The contribution of alloy storage to total capacity is always larger than the conversion storage indicating the superiority of the former. The formation of crystalline Sb(Al) is noted in Sb_1.9Al_0.1S₃, unlike amorphous Sb in Sb₂S₃. Retention of the nanorod microstructure in Sb_1.9Al_0.1S₃ despite the volume expansion enhances the performance. On the contrary, the Sb₂S₃ nanorod electrode gets pulverized and the surface shows microcracks. Percolating Sb nanoparticles buffered by the Li₂S matrix and other polysulfides enhance the performance of the electrode. These studies pave the way for high-energy and high-power density LIBs with alloy anodes.